Taxonomy term

aftershock

Earthquake aftershocks may be more unpredictable than previously thought. Researchers studying past quakes say they have identified a new class of aftershocks that can occur within seconds to minutes after the mainshock on neighboring faults.

Can a large earthquake trigger another quake hundreds or even thousands of kilometers away? The answer, scientists say, appears to be yes, but when it happens is far from predictable. How does such dynamic triggering affect global earthquake hazards? Perhaps the whole world should be considered an aftershock zone.

On Feb. 27, 2010, a magnitude-8.8 earthquake struck the subduction zone off the coast of Chile. The resulting Rayleigh surface waves rippled around the world, triggering small earthquakes in many different tectonic settings, including Antarctica. As the surface waves moved across the white continent, a third of Antarctic seismic stations reported shaking coming from so-called “ice quakes.”

During the past year, many of the 386,000 inhabitants of New Zealand’s second-largest city, Christchurch, have thought and said one phrase over and over again: “When will it stop?” Starting in September 2010, several major earthquakes and more than 8,000 aftershocks have rocked the city and region. Rebuilding has started, been interrupted, started again and been halted again. People have been living without water, sewer, roads, offices and homes for so long that it may be hard to remember what “normal” is.